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    <title>Document</title>
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<script>
    function strConvert(str){
        let arr=[];
        for(let i=0;i<str.length;i++){
            if(str[i]>="a"&&str[i]<="z"){
                arr.push(str[i].toUpperCase());
            }else{
                arr.push(str[i].toLowerCase());
            }
        }
        return arr.join("");
    }
    let str="awoViEGfhFEwof";
    console.log(strConvert(str));
    
</script>